In general, an ellipsometer is a measuring device which obtains optical properties of a sample by measuring a change in a polarizing state after light having a specific polarizing state is incident to a surface of the sample and reflected from it, and then analyzing the measured values. Particularly, in the semiconductor industrial field using various manufacturing methods of nano thin film, the ellipsometer is widely used as a non-destructive and non-contacted real-time measuring technology for estimating physical properties of the manufactured nano thin films. Typically, the ellipsometer obtains data about an angle change relevant to the amplitude of light reflected from the sample.
A conventional ellipsometer can be applied to a semiconductor sample, but can not be applied to a biomaterial like protein. Preferably, a surface plasmon resonance (SPR) sensor is used for measure the properties of the biomaterial.
Electrons on a surface of a metal are collectively vibrated by normal directional vibration with respect to the surface of the metal, and this motion is called ‘surface plasmon wave’. The vibration of quantized electrons is the surface plasmon. In order to quantitatively analyze a material using a phenomenon that the surface plasmon is excited by light waves, there have been proposed various SPR sensors.
The resonance phenomenon of the surface plasmon is applied to a polarizer, or mainly applied to a bio-sensor, i.e., an opto-chemical sensor by using sensitivity with respect to polarizing characteristic of light.
A sensor using a resonance absorbing effect of the surface plasmon, i.e., a surface plasmon sensor is used for measuring a change in a concentration, a thickness or a refractive index of a dielectric substance contacted with the surface of the metal, and also may be used as a bio-sensor for measuring a change in a concentration of a sample like a bio material in real time without labeling.
FIG. 1 shows an example of a conventional SPR sensor.
As shown in the drawing, the SPR sensor includes a light source 110, a polarizer 120 for polarizing light emitted from the light source 110, a prism 130 in which the polarized light is incident and then reflected, a glass substrate 140 which is provided on one surface of the prism 130 and to which the polarized light passing through the prism 130 is incident, a metal thin film 150 which is coated on the glass substrate 140 with a few tens nanometer-sized thickness so that the polarized light passing through the glass substrate 140 is reflected by surface plasmon resonance, and a light receiving part 160 for detecting the light reflected by the metal thin film and passed through the glass substrate 140 and the prism 130. Meanwhile, the metal thin film is contacted with a sample 170. If the concentration, thickness or refractive index of the sample 170 is changed between the metal thin film 150 and the sample 170, conditions of the SPR are correspondingly changed. Thus, the quantity of light reflected to the light receiving part 160 is changed, and the change in the concentration of the sample 170 contacted with the metal thin film 150 is measured by using this phenomenon.
A conventional SPR sensor only using reflexibility measures an intensity of light or a change in angle which designates the minimal reflexibility. But a surface plasmon resonance (SPR) sensor using ellipsometry can obtain phase information as well as amplitude of light corresponding to reflexibility information. Particularly, since an ellipsometric phase change is sensitive under an optimal SPR condition, it is possible to obtain high sensitive measurement precision.
Especially, when a low molecular material used as a new drug candidate is conjugated to target protein, it is required to provide the extremely sensitive measurement precision. In the optimal SPR condition, it is possible to improve the measurement precision by measuring the ellipsometric phase change.